1. Field of the Invention
The present invention relates to A.C. power supplies for supplying power to audio signal generating and transmission equipment in general and in particular to a method and apparatus comprising a filter and power factor compensation network for providing a low and stable, i.e. resistive, impedance to frequencies above 60 Hz and maximizing the efficiency at which power is delivered to such equipment at 60 Hz.
2. Description of the Related Art
Certain audio equipment is sensitive to high frequency noise induced fluctuations in the impedance of a conventional 60 Hz power source providing power to the equipment. This sensitivity can adversely affect the quality, e.g. fidelity or clarity, of and generate noise in the audio signals being propagated in the equipment.
Audio equipment is also sensitive to the amount of power being delivered to the equipment. If too little power is delivered, the dynamic range of the equipment is degraded.
The amount or magnitude of the power delivered to a load is defined by the equation EQU Power=EI Cosine .phi.
where Cosine .phi. is defined as the power factor and .phi. is the angle between the applied voltage E and current I.
Audio equipment, such as amplifiers, tape decks, compact disc players, etc., comprise inductive loads including input power transformers and/or motors which typically produce a phase shift between the applied voltage E and current I and consequently a power factor of less than 1 in the circuit supplying the power. Heretofore, no method or apparatus has been generally available to operators of audio equipment for use in compensating for a low power factor or for adjusting the power factor for different inductive loads presented by audio equipment coupled to a source of 60 Hz power.